Car battery life - How long did your battery last?

This is a discussion on Car battery life - How long did your battery last? within Technical Stuff, part of the Under the Hood category; I can briefly relate my experience over 40 years of using batteries in cars.
When I owned my first car(given ...

I can briefly relate my experience over 40 years of using batteries in cars.
When I owned my first car(given by my father after about 2 years of use) a Fiat in 1969 the original battery when replaced lasted 2.0 years. Subsequently, I put an alternator in the car (jugaad but properly done - Presolite alternator) when I replaced the battery. The battery with some care in ensuring electrolyte level lasted 4.5 years. This is the best I've ever got and was short distance running mostly. When I switched to a new Maruti 800 the battery lasted around 2.2 years and thereafter almost without fail the average battery life has been 2.5 years or a little more. This was in an Esteem, Honda City (1st, 2nd and 3rd generation), old Baleno etc. The best I got in the last 10 years was 3.5 years in my Honda City ivtech. My own experience is that the battery does go suddenly without much warning. This is because the electronics are more sophisticated now and below a threshold voltage the car will not start. This is especially true if you have anti-theft systems installed. In the older cars one could get away with a battery that was showing lower voltage with groaning and grinding starter motors.